The present invention relates to methods and apparatuses for controlling or regulating the flow of fluids, more particularly to valves for stopping and starting fluid flow, such as ball valves.
Valves are devices that are used for controlling the flow of fluid. There are several categories of valves, such as stop valves, check valves, pressure-control valves and thermostatic recirculating valves. Of particular interest herein are stop valves, which are used to partially or completely shut off fluid flow, and which generally involve fluid control via movement of a valve member such as a valve stem. Among the various types of stop valves are ball valves, globe valves, gate valves, plug valves, needle valves and butterfly valves.
Ball valves are stop valves according to which a ball having a hole (e.g., axial bore) provided therethrough is used for stopping or starting fluid flow. To open the ball valve, the ball is rotated to a position wherein the ball's hole is aligned with both the inlet and the outlet of the valve body. To close the ball valve, the ball is rotated to a position wherein the hole is perpendicular to both the inlet and the outlet of the valve body. Frequently, a valve handle or planetary gearing is used to effect a ninety degree turn, either for rotating the ball from a closed position to an open position or, conversely, for rotating the ball from an open position to a closed position. Ball valves have been used in fluid systems that require a high-pressure drop across the valve when opening.
Ball valves are excellent for most piping systems, as they provide minimal restriction to flow when fully open and a positive stop when closed. When the ball valve is opened with a high pressure on one side and a low pressure on the other side, a noise is generated during opening. As the ball rotates, it exposes a small flow passage area that gradually increases with continued rotation. The noise that is generated in the short time during which the opening takes place is significantly greater relative to the steady state flow noise that occurs after the ball valve is fully open. Thus, unwanted noise is associated with the opening of a ball valve under such circumstances wherein a high-pressure source exists on one side of the ball valve and the fluid leads to a low-pressure region on the opposite side of the ball valve.
Nor do quiet throttling valves provide a satisfactory solution to the above-described noise difficulty characterizing piping systems. Throttling valves typically are characterized by fluid path tortuosity. For instance, according to current technology of quiet throttling valves used at the Naval Surface Warfare Center, Carderock Division (NSWCCD), the fluid flow is opened to a tortuous path of a series of orifices on multiple disk stacks. This tortuous path reduces flow noise associated with fluid cavitation, which occurs as a result of a large pressure drop, by dividing up the pressure drop into a series of small pressure drops. Flow path in the quiet throttling valve is always through the disk stacks. This is undesirable in shipboard fluid systems since, in comparison with a full-open ball valve, there is a significant increase in (i) the time required to move a fluid from one location to another and (ii) the restriction in the system.
Incorporated herein by reference are the following United States patents relating to valve technology: Ryerson et al. U.S. Pat. No. 6,408,871 B1 issued Jun. 25, 2002; Baumann U.S. Pat. No. 6,244,297 B1 issued Jun. 12, 2001; Tuttle U.S. Pat. No. 6,109,591 issued Aug. 29, 2000; McCarty et al. U.S. Pat. No. 6,095,196 issued Aug. 1, 2000; Wears et al. U.S. Pat. No. 6,026,859 issued Feb. 22, 2000; Baumann et al. U.S. Pat. No. 5,941,281 issued Aug. 24, 1999; Knop et al. U.S. Pat. No. 5,921,275 issued Jul. 13, 1999; Lebo et al. U.S. Pat. No. 5,819,803 issued Oct. 13, 1998; Baumann et al. 5,769,122 issued Jun. 23, 1998; Greer U.S. Pat. No. 5,370,154 issued Dec. 6, 1994; Vick U.S. Pat. No. 4,458,718 issued Jul. 10, 1984; Seger U.S. Pat. No. 4,279,274 issued Jul. 21, 1981; Vick U.S. Pat. No. 3,978,891 issued Sep. 7, 1976; Hayner et al. U.S. Pat. No. 3,688,800 issued Sep. 5, 1972.